Voltage scaling of ferroelectric thin films deposited by CVD

Abstract

Abstract For many applications of ferroelectric ICs it is desirable to operate ferroelectric memory at the lowest possible power and voltage. One way to reduce the operating voltage is to reduce film thickness. We report on the electrical properties of MOCVD deposited PZT 40/60 and 20/80 films as a function of film thickness. As the thickness is reduced, switched polarization at saturation (P∗-P⁁) is reduced, but the coercive E-field is not substantially changed. Films also have imprint and fatigue behavior that is independent of film thickness when operated at constant electric field. For films below 60nm the leakage current rises rapidly; this is likely due to the effects of film roughness. For 65nm films of the PZT 20/80 material, we observed well formed hysteresis loops and PSW > 55μC/cm2 at 1.2V; polarization was greater than 90% saturated at that voltage.